When I eagerly walked into my current role nearly 2 years ago, I was staggered by the number of linked servers (often 5 or 6 instances of 3 different linked servers in one query).
The company had never had a DBA before and when they hit performance issues they just purchased another server and moved databases to another set of hardware... little realising that network I/O is your slowest resource.
I'm slowly dragging systems back from the dark ages and the number of network blips we have is much better. but I've had to patch a few things while we work to get it better - replication has been my friend, - slow gentle dribbles of data that I can use locally rather than query 100,000 records via a linked server... it's not a fix, but it keeps my query times down
Our network team very rarely let us down, it's our code architecture that puts pressure on our network (which we have to share with email, fielshare etc etc) - yesterday we had a 2 minute network outage... I lost all of my current connections to SQL and all of our linked servers failed - but some of my colleagues were more concerned that facebook was not available 🙁